From: "Wu, Feng" <feng.wu@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Wu, Feng" <feng.wu@intel.com>
Subject: RE: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked
Date: Fri, 19 Dec 2014 02:51:46 +0000 [thread overview]
Message-ID: <E959C4978C3B6342920538CF579893F00230ABD1@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <54929240.6050306@redhat.com>
> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org
> [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Paolo Bonzini
> Sent: Thursday, December 18, 2014 4:37 PM
> To: linux-kernel@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org; kvm@vger.kernel.org;
> linux-kernel@vger.kernel.org; kvm@vger.kernel.org
> Subject: Re: [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU
> is blocked
>
>
>
> On 18/12/2014 04:16, Wu, Feng wrote:
> >>> pre-block:
> >>> - Add the vCPU to the blocked per-CPU list
> >>> - Clear 'SN'
> >>
> >> Should SN be already clear (and NV set to POSTED_INTR_VECTOR)?
> >
> > I think the SN bit should be clear here, Adding it here is just to make sure
> > SN is clear when vCPU is blocked, so it can receive wakeup notification event
> later.
>
> Then, please, WARN if the SN bit is set inside the if (vcpu->blocked).
> Inside that if you can just add the vCPU to the blocked list on vcpu_put.
>
> >> Can it
> >> happen that you go from sched-out to blocked without doing a sched-in
> first?
> >>
> >
> > I cannot imagine this scenario, can you please be more specific? Thanks a lot!
>
> I cannot either. :) But it would be the case where SN is not cleared.
> So we agree that it cannot happen.
>
> >> In fact, if this is possible, what happens if vcpu->preempted &&
> >> vcpu->blocked?
> >
> > In fact, vcpu->preempted && vcpu->blocked happens sometimes, but I think
> there is
> > no issues. Please refer to the following case:
>
> I agree that there should be no issues. But if it can happen, it's better:
>
> 1) to separate the handling of preemption and blocking: preemption
> handles SN/NV/NDST, blocking handles the wakeup list.
>
Sorry, I don't quite understand this.
I think handling of preemption and blocking is separated in vmx_vcpu_put().
For vmx_vcpu_load(), the handling of SN/NV/NDST is common for preemption
and blocking.
Thanks,
Feng
> 2) to change this
>
> + } else if (vcpu->blocked) {
> + /*
> + * The vcpu is blocked on the wait queue.
> + * Store the blocked vCPU on the list of the
> + * vcpu->wakeup_cpu, which is the destination
> + * of the wake-up notification event.
>
> to just
>
> }
> if (vcpu->blocked) {
> ...
> }
> > kvm_vcpu_block()
> > -> vcpu->blocked = true;
> > -> prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
> >
> > before schedule() is called, this vcpu is woken up by another guy, so
> > the state of the vcpu associated thread is changed to TASK_RUNNING,
> > then preemption happens after interrupts or the following schedule() is
> > hit, this will call kvm_sched_out(), in which current->state ==
> TASK_RUNNING
> > and vcpu->preempted is set to true. So now vcpu->preempted and
> vcpu->blocked
> > are both true. In vmx_vcpu_put(), we will check vcpu->preempted first, so
> > the vCPU will not be blocked, and the vcpu->blocked will be set the false in
> > vmx_vcpu_load().
> >
> > But maybe I need do a little change to the vmx_vcpu_load() like below:
> >
> > /*
> > * Delete the vCPU from the related wakeup queue
> > * if we are resuming from blocked state
> > */
> > if (vcpu->blocked) {
> > vcpu->blocked = false;
> > + /* if wakeup_cpu == -1, the vcpu is currently not
> blocked on any
> > + pCPU, don't need dequeue here */
> > + if (vcpu->wakeup_cpu != -1) {
> >
> spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,
> > vcpu->wakeup_cpu), flags);
> > list_del(&vcpu->blocked_vcpu_list);
> >
> spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,
> > vcpu->wakeup_cpu), flags);
> > vcpu->wakeup_cpu = -1;
> > + }
> > }
>
> Good idea.
>
> Paolo
>
> > Any ideas about this? Thanks a lot!
> >
> > Thanks,
> > Feng
> >
> >
> > -> schedule();
> >
> >
> >>
> >>> - Set 'NV' to POSTED_INTR_WAKEUP_VECTOR
> >>>
> >>> post-block:
> >>> - Remove the vCPU from the per-CPU list
> >>
> >> Paolo
> >>
> >>> Signed-off-by: Feng Wu <feng.wu@intel.com>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe kvm" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2014-12-19 2:53 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-12 15:14 [v3 00/26] Add VT-d Posted-Interrupts support Feng Wu
2014-12-12 15:14 ` [v3 01/26] genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a VCPU Feng Wu
2014-12-12 15:14 ` [v3 02/26] iommu: Add new member capability to struct irq_remap_ops Feng Wu
2015-01-28 15:22 ` David Woodhouse
2015-01-29 8:34 ` Wu, Feng
2014-12-12 15:14 ` [v3 03/26] iommu, x86: Define new irte structure for VT-d Posted-Interrupts Feng Wu
2015-01-28 15:26 ` David Woodhouse
2014-12-12 15:14 ` [v3 04/26] iommu, x86: Implement irq_set_vcpu_affinity for intel_ir_chip Feng Wu
2015-01-28 15:26 ` David Woodhouse
2015-01-29 7:55 ` Wu, Feng
2014-12-12 15:14 ` [v3 05/26] x86, irq: Implement irq_set_vcpu_affinity for pci_msi_ir_controller Feng Wu
2014-12-12 15:14 ` [v3 06/26] iommu, x86: No need to migrating irq for VT-d Posted-Interrupts Feng Wu
2014-12-18 14:26 ` Zhang, Yang Z
2014-12-19 1:40 ` Wu, Feng
2014-12-19 1:46 ` Zhang, Yang Z
2014-12-19 11:59 ` Paolo Bonzini
2014-12-23 0:37 ` Zhang, Yang Z
2014-12-23 8:47 ` Paolo Bonzini
2014-12-23 9:07 ` Wu, Feng
2014-12-23 9:34 ` Paolo Bonzini
2014-12-24 1:38 ` Zhang, Yang Z
2014-12-24 2:12 ` Jiang Liu
2014-12-24 2:32 ` Zhang, Yang Z
2014-12-24 3:08 ` Wu, Feng
2014-12-24 4:04 ` Zhang, Yang Z
2014-12-24 4:54 ` Jiang Liu
2015-01-28 15:29 ` David Woodhouse
2014-12-12 15:14 ` [v3 07/26] iommu, x86: Add cap_pi_support() to detect VT-d PI capability Feng Wu
2015-01-28 15:32 ` David Woodhouse
2014-12-12 15:14 ` [v3 08/26] iommu, x86: Add intel_irq_remapping_capability() for Intel Feng Wu
2015-01-28 15:37 ` David Woodhouse
2015-01-29 8:57 ` Wu, Feng
2014-12-12 15:14 ` [v3 09/26] iommu, x86: define irq_remapping_cap() Feng Wu
2014-12-12 15:14 ` [v3 10/26] KVM: change struct pi_desc for VT-d Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 11/26] KVM: Add some helper functions for Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 12/26] KVM: Initialize VT-d Posted-Interrupts Descriptor Feng Wu
2014-12-18 15:19 ` Zhang, Yang Z
2014-12-12 15:14 ` [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI Feng Wu
2014-12-18 14:49 ` Zhang, Yang Z
2014-12-18 16:58 ` Paolo Bonzini
2014-12-19 1:13 ` Zhang, Yang Z
2014-12-19 1:30 ` Wu, Feng
2014-12-19 1:30 ` Wu, Feng
2014-12-19 1:47 ` Zhang, Yang Z
2014-12-19 11:59 ` Paolo Bonzini
2014-12-19 23:48 ` Wu, Feng
2014-12-20 13:16 ` Paolo Bonzini
2014-12-22 4:48 ` Wu, Feng
2014-12-22 9:27 ` Paolo Bonzini
2014-12-22 11:04 ` Wu, Feng
2014-12-22 11:06 ` Paolo Bonzini
2014-12-22 11:17 ` Wu, Feng
2014-12-22 11:23 ` Paolo Bonzini
2014-12-22 14:13 ` Yong Wang
2015-01-09 14:54 ` Radim Krčmář
2015-01-09 14:56 ` Paolo Bonzini
2015-01-09 15:12 ` Radim Krčmář
2015-01-09 15:18 ` Paolo Bonzini
2015-01-09 15:47 ` Radim Krčmář
2015-01-13 0:27 ` Wu, Feng
2015-01-13 16:17 ` Radim Kr?má?
2015-01-14 1:27 ` Wu, Feng
2015-01-14 13:02 ` Paolo Bonzini
2015-01-14 16:59 ` Radim Kr?má?
2015-01-20 21:04 ` Nadav Amit
2015-01-21 21:16 ` Radim Kr?má?
2014-12-12 15:14 ` [v3 14/26] KVM: Get Posted-Interrupts descriptor address from struct kvm_vcpu Feng Wu
2014-12-12 15:14 ` [v3 15/26] KVM: add interfaces to control PI outside vmx Feng Wu
2014-12-12 15:14 ` [v3 16/26] KVM: Make struct kvm_irq_routing_table accessible Feng Wu
2014-12-17 16:17 ` Paolo Bonzini
2014-12-19 2:19 ` Wu, Feng
2014-12-19 11:59 ` Paolo Bonzini
2014-12-19 23:39 ` Wu, Feng
2014-12-12 15:14 ` [v3 17/26] KVM: make kvm_set_msi_irq() public Feng Wu
2014-12-17 17:32 ` Paolo Bonzini
2014-12-12 15:14 ` [v3 18/26] KVM: kvm-vfio: User API for VT-d Posted-Interrupts Feng Wu
2014-12-12 15:14 ` [v3 19/26] KVM: kvm-vfio: implement the VFIO skeleton " Feng Wu
2014-12-12 15:14 ` [v3 20/26] KVM: x86: kvm-vfio: VT-d posted-interrupts setup Feng Wu
2014-12-12 15:14 ` [v3 21/26] x86, irq: Define a global vector for VT-d Posted-Interrupts Feng Wu
2014-12-18 14:54 ` Zhang, Yang Z
2014-12-19 0:52 ` Wu, Feng
2015-01-30 18:18 ` H. Peter Anvin
2015-02-02 1:06 ` Wu, Feng
2015-02-23 22:04 ` Marcelo Tosatti
2014-12-12 15:14 ` [v3 22/26] KVM: Define a wakeup worker thread for vCPU Feng Wu
2014-12-12 15:14 ` [v3 23/26] KVM: Update Posted-Interrupts Descriptor when vCPU is preempted Feng Wu
2014-12-17 17:11 ` Paolo Bonzini
2014-12-18 3:15 ` Wu, Feng
2014-12-18 8:32 ` Paolo Bonzini
2014-12-19 2:09 ` Wu, Feng
2015-02-23 22:21 ` Marcelo Tosatti
2015-03-02 9:12 ` Wu, Feng
2014-12-12 15:14 ` [v3 24/26] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked Feng Wu
2014-12-17 17:09 ` Paolo Bonzini
2014-12-18 3:16 ` Wu, Feng
2014-12-18 8:37 ` Paolo Bonzini
2014-12-19 2:51 ` Wu, Feng [this message]
2015-02-25 21:50 ` Marcelo Tosatti
2015-02-26 8:08 ` Wu, Feng
2015-02-26 23:41 ` Marcelo Tosatti
2015-02-26 23:40 ` Marcelo Tosatti
2015-03-02 13:36 ` Wu, Feng
2015-03-04 12:06 ` Marcelo Tosatti
2015-03-06 6:51 ` Wu, Feng
2015-03-12 1:15 ` Marcelo Tosatti
2015-03-16 11:42 ` Wu, Feng
2015-03-25 23:17 ` Marcelo Tosatti
2015-03-27 6:34 ` Wu, Feng
2015-03-27 19:30 ` Marcelo Tosatti
2015-03-30 4:46 ` Wu, Feng
2015-03-30 23:55 ` Marcelo Tosatti
2015-03-31 1:13 ` Wu, Feng
2015-04-14 7:37 ` Wu, Feng
2015-06-05 21:59 ` Marcelo Tosatti
2015-06-08 1:43 ` Wu, Feng
2014-12-12 15:14 ` [v3 25/26] KVM: Suppress posted-interrupt when 'SN' is set Feng Wu
2014-12-17 17:42 ` Paolo Bonzini
2014-12-18 3:14 ` Wu, Feng
2014-12-18 8:38 ` Paolo Bonzini
2014-12-18 15:09 ` Zhang, Yang Z
2014-12-19 2:58 ` Wu, Feng
2014-12-19 3:32 ` Zhang, Yang Z
2014-12-19 4:34 ` Wu, Feng
2014-12-19 4:44 ` Zhang, Yang Z
2014-12-19 4:49 ` Wu, Feng
2014-12-19 5:25 ` Zhang, Yang Z
2014-12-19 5:46 ` Wu, Feng
2014-12-19 7:04 ` Zhang, Yang Z
2014-12-19 12:00 ` Paolo Bonzini
2014-12-19 23:34 ` Wu, Feng
2014-12-12 15:15 ` [v3 26/26] iommu/vt-d: Add a command line parameter for VT-d posted-interrupts Feng Wu
2015-01-28 15:39 ` David Woodhouse
2014-12-16 9:04 ` [v3 00/26] Add VT-d Posted-Interrupts support Wu, Feng
2015-01-06 1:10 ` Wu, Feng
2015-01-09 12:46 ` joro
2015-01-09 13:58 ` Wu, Feng
2015-01-21 2:25 ` Wu, Feng
2015-01-28 3:01 ` Wu, Feng
2015-01-28 3:44 ` Alex Williamson
2015-01-28 4:44 ` Wu, Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E959C4978C3B6342920538CF579893F00230ABD1@SHSMSX104.ccr.corp.intel.com \
--to=feng.wu@intel.com \
--cc=iommu@lists.linux-foundation.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).